Is paper missing or is it a simple tear? I would probably post it as either of these, being small, is allowed. A simple tear I would attempt to repair with a tiny amount of white glue on the edges of the paper fiber, protect with a fold of wax paper or backing from a sticker, clamped shut as it dries. That usually renders a tear invisible.

Pretty sure the rules say a less than 1" tear is okay. I'd just tape over it and send it out.

I got a new book from someone in a game, directly from the bookseller. It came with a tear in the cover! I just put some tape on the tear (it's less than an inch) and I won't hesitate to send the book out again since it's a brand new book, read once.